James McAvoy confused by some roles

James McAvoy sometimes finds himself in roles where he ''doesn't know what the f**k'' he's going to do.

The actor admits he can't always envision a part just by reading the script, but he gets a great feeling when one immediately leaps out at him, such as his current film, 'Filth'.

He said: ''Sometimes when you read a script you don't start getting ideas and that can be slightly worrying. I have done jobs where I think, 'I don't know what the f**k I'm going to do,' and you just get there on the day and make it work. But with 'Filth' every single scene just presented so many ideas and I was inspired immediately.''

Hollywood star James - who has appeared in hits including 'X Men: First Class', 'The Last King of Scotland' and 'Trance' - also knows his name can help films gain backing, but he trusted 'Filth' director Jon S. Baird as soon as he met him.

He added: ''Sometimes filmmakers want you just because they think you can help get things financed. [But] sometimes you just get a feeling and I trusted Jon. He is very strong, very bold and very direct, bull***t is not part of his makeup. So I thought, 'He's definitely the guy to direct this because you need someone brave and bold.''